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Geron (NASDAQ:GERN)
Q4 2020 Earnings Call
Mar 11, 2021, 4:30 p.m. ET

Contents:

  • Prepared Remarks
  • Questions and Answers
  • Call Participants

Prepared Remarks:


Operator

Ladies and gentlemen, thank you for standing by, and welcome to the fourth-quarter 2020 Geron earnings conference call. [Operator instructions] I would now like to hand the conference over to Olivia Bloom, Geron's chief financial officer. Thank you. Please go ahead, ma'am.

Olivia Bloom -- Chief Financial Officer

Thank you, Erica, and good afternoon, everyone. Thank you for joining us for today's conference call. I'm joined today by Dr. John Scarlett, Geron's chairman and chief executive officer; and Aleksandra Rizo, our chief medical officer.

After the market close today, we announced our fourth quarter and year-end 2020 financial results and operational highlights via press release, which is available on our website under geron.com/investors. In addition, a live webcast of this call is available on our website, and an archive will be available for 30 days. Before we begin, please note that this presentation and question-and-answer session will contain forward-looking statements relating to Geron's plans, expectations, timelines, beliefs, statements of potentiality and projections. These include, without limitation, those regarding the expected time lines for completion of enrollment and the results from the IMerge phase three and IMpactMF clinical trials and submission of an NDA, the potential for positive outcomes from IMerge phase three and IMpactMF, potential approval imetelstat by regulatory authorities and commercialization of imetelstat, the expectation that Geron's current financial resources will be sufficient to fund its operations until the end of 2022, and that imetelstat has the potential to be disease-modifying and alter the course of MDS and MF.

These and other forward-looking statements involve risks and uncertainties that can cause actual results to differ materially from those in such forward-looking statements. These risks and uncertainties include, without limitations, those regarding that the company may be unable to overcome all the enrollment, clinical, safety, efficacy, technical, scientific, operational, manufacturing and regulatory challenges to meet the expected time line for IMerge phase three and IMpactMF due to COVID or otherwise; that in the phase three clinical trial, imetelstat may not prove to be as safe or efficacious as in the phase two trial and may not demonstrate that it is safe, efficacious and disease modifying; that regulatory authorities may not permit the further development of imetelstat on a timely basis or at all and may not approve it for commercialization; and that Geron may need additional financial resources before the end of 2022 for the development and commercialization of imetelstat. Detailed information on the above risks and uncertainties and additional risks, uncertainties and factors that could cause actual results to differ materially from those in the forward-looking statements are explained under the heading Risk Factors in Geron's annual report on Form 10-K for the year ended December 31, 2020, filed with the Securities and Exchange Commission. Undue relied should not be placed on forward-looking statements which speak only as of the date they are made, and the facts and assumptions underlying the forward-looking statements may change.

On today's call, Dr. Scarlett will make a few introductory comments, after which, I will cover the fourth quarter and year-end financial results, as well as guidance for 2021. Dr. Rizo will provide clinical development update on the ongoing IMerge phase three trial in our target patient population with low or Intermediate-1 risk myelodysplastic syndrome, which we call low-risk MDS, who are transfusion-dependent non-del(5q) and relapsed after or refractory to prior treatment with an erythropoiesis-stimulating agent or ESA.

she will also provide an update on our IMpactMF phase three trial, which is in a population of patients with intermediate to or high-risk myelofibrosis who are refractive to prior treatment with a JAK inhibitor, which we call refractory MF. Aleksandra will also discuss how the data and analyses we reported at the American Society of Hematology Annual Meeting in December 2020 has deepened our understanding on imetelstat's mechanism of action and its effect on the underlying cause of the disease and the indications we're pursuing. Dr. Scarlett will then comment on the evolving lower-risk MDS and MF market and imetelstat's positioning in those markets given its potentially highly differentiated product profile.

He'll finish the call with closing remarks on planned milestones for 2021. I'll now turn the call over to Dr. Scarlett, Geron's chairman and CEO. Chip?

John Scarlett -- Chairman and Chief Executive Officer

Thanks, Olivia. I'd like to welcome everyone to our fourth quarter and year-end 2020 conference call. Let me start by sharing our vision for Geron, which is to become a leader in the treatment of hematologic malignancies, by changing the course of these diseases, thereby improving and extending the lives of patients. As I look back on 2020, we made significant progress toward realizing this vision.

So again, we presented compelling and differentiating data from our IMerge phase two lower-risk MDS trial. These data showed high rates and exceptional durability of transfusion independence. Of any study in non-del(5q) lower-risk MDS patients who relapsed and refractory to ESAs, the 20-month minimum duration of transfusion independence in IMerge phase two was the longest reported to date. In our IMerge phase three lower-risk MDS study, enrollment gains continued with over 50% enrollment achieved by the end of the year.

We also presented exceptional overall survival data from our IMbark phase two trial in JAK eye relapsed or refractory MF patients. In this trial, imetelstat treated patients had a median OS of 28 months, which is almost twice the median OS reported in the medical literature. Certain other supporting data and after conferring with FDA, we opened IMpactMF, our phase three trial in JAK eye refractory MF patients. IMpactMF is the first and to date only phase three trial with overall survival as the primary endpoint.

We also presented strong evidence of disease-modifying [Inaudible] of low-risk MDS and relapsed/refractory MF. In both indications, we saw reductions in key driver mutations of the underlying disease. Furthermore, imetelstat is the only drug in development to establish a correlation of these and other measures of disease modification with key clinical outcomes, including durability of transfusion independence and low-risk MDS and improvement in MF. Such correlations have given us even greater confidence in the potential positive outcomes for our ongoing phase three IMpactMF trials [Inaudible] doesn't stand out as important accomplishments in 2020.

The first was that we successfully established our global imetelstat supply chain, ensuring uninterrupted drug supply for clinical trials and permitting inclusion of Geron manufactured materials in our two phase three trials. Second, we raised over $175 million in new capital from both an underwritten public offering and a new loan facility. As a result, we expect our current cash will be sufficient to fund our operations through the end of 2022. All of these accomplishments were made despite the challenges posed by the ongoing COVID effect on clinical trial.

[Inaudible], And as of today, we've achieved 65% enrollment. As a result of the COVID pandemic, ongoing enrollment continues to be challenging. These enrollment challenges have been due primarily to the reluctance of patients to participate in clinical trials and, as well as delays in opening new sites. These effects of the pandemic appear to be true for many oncology trials, not just ours.

In addition, we believe enrollment in IMerge phase three may be starting to be impacted by luspatercept becoming more widely available as a treatment for patients who are RS+ in lower-risk MDS. From everything we can see, the enrollment constraints in this trial are not a result of IMerge being inadequately prioritized by investigators. And our interactions with them, our investigators remain enthusiastic about our imetelstat data and are committed to enrolling their patients in this trial. Based on the information we currently have, we expect IMerge phase three to be fully enrolled in the second half of 2021.

Depending on the exact timing when that full enrollment is achieved, we expect top line results from IMerge phase three to be available from the end of 2022 to the first half of 2023. Aleksandra will discuss in more detail the initiatives we put in place to improve enrollment in the face of pandemic. She'll also update our activities in the conduct of IMpactMF. We currently expect the interim analysis for IMpactMF to occur in 2024 and the final analysis to occur in 2025.

Looking ahead, our planned strategic priorities for the next three years.

Olivia Bloom -- Chief Financial Officer

John?

John Scarlett -- Chairman and Chief Executive Officer

And commercially launching this highly differentiated drug in low-risk MDS. Now I'd like to hand the call -- I'd like to call -- hand the call over. Go ahead.

Olivia Bloom -- Chief Financial Officer

I'm sorry. You were breaking up a bit just back there just right before for Aleksandra?

John Scarlett -- Chairman and Chief Executive Officer

OK. So we currently expect the interim analysis for IMpactMF to occur in 2024 and the final analysis to occur in 2025. Looking ahead, our planned strategic priorities for the next three years include achieving top line results in IMerge phase three, gaining regulatory approval of imetelstat and commercially launching this highly differentiated drug in lower-risk MDS. Now I'd like to hand the call over to Olivia to discuss our fourth quarter and year-end financial results and financial guidance for 2021.

Olivia?

Olivia Bloom -- Chief Financial Officer

Thank you, John. As of December 31, 2020, we had approximately $260 million in cash, cash equivalents and current and non-current marketable securities. Our cash position reflects net proceeds of approximately $140 million from a public offering in May 2020 and approximately $24 million in initial net proceeds from a non-dilutive $75 million loan facility that we closed at the end of the third quarter last year. Based on current planning assumptions, we estimate our current financial resources to be sufficient for our operations until the end of 2022.

Overall, the financial results for the fourth quarter and year-to-date period were in line with our expectations and our operating expense guidance. Operating expenses for the three and 12 months ended December 31, 2020, were generally higher in comparison to the same period in 2019, due to head count increases in 2019 and 2020 across the company, increased activity for the IMerge phase three clinical trial in low-risk MDS, start-up activities for the IMpactMF phase three clinical trial in refractory MF and costs associated with ongoing imetelstat manufacturing. These increased costs were partially offset by lower costs related to purchases of raw materials, drug substance and drug products and completion of the IMbark clinical trial. Regarding financial guidance for 2021, we expect our operating expense burn to range from $108 million to $112 million, which includes costs for our two ongoing phase three clinical trials, production of validation batches of imetelstat at contract manufacturers to enable future production of imetelstat for clinical and commercial purposes and preparatory activities for NDA and commercial readiness.

Financial guidance is based on a set of assumptions at a point in time, and if the company's plans change, causing assumptions to be revised, then we will update guidance at that time. With that, I will now turn the call over to Aleksandra to provide an update on our phase three clinical development activity. Aleksandra?

Aleksandra Rizo -- Chief Medical Officer

Thanks, Olivia. Good afternoon, everyone. As Chip mentioned, we have now achieved 65% enrollment in our IMerge phase three trial. Also, the first meeting of the independent data monitoring committee was held in December, and the IDMC recommended that the trial continue without modification.

We expect the enrollment boosting activities we started last year to become more effective as COVID cases decline and as clinical operations begin to hopefully return to normal over the next several months. As a result, we believe the clinical science liaisons were engaged in the beginning of last year will be able to interact with clinical sites more easily and with greater frequency to help alert site personnel and patients to the potential benefits of participating in IMerge phase three. In addition, we believe our social media campaign will help drive patient recruitment. Over the next few months, we expect all of the approximately 20 additional sites for IMerge will be open, bringing the total number of sites in this trial to approximately 120.

Of course, the best boost to enrollment should come as vaccinations proceed, the number and severity of COVID cases decline and patients, again, become more comfortable leaving their homes to participate in clinical trials. Earlier in this call, Chip mentioned kind of the more mature clinical data from our IMerge phase two trial in low-risk MDS, on which I would like to expand on briefly. These data are very encouraging. And we continue to differentiate imetelstat from other currently approved or investigational treatments.

Foremost, imetelstat achieved its remarkable durability for transfusion independence. In addition to those 42% of patients that achieved the primary endpoint of eight-week transfusion independent, 32% of the imetelstat patients were transfusion free for 24 weeks, which was a key secondary endpoint. Furthermore, 29% of the patients were transfusion free for over a year. We also reported a median duration of transfusion independence of 20 months.

That compares very favorably to the most recent available data we've seen from luspatercept in which a median duration of transfusion independence of seven months was reported. I'd also like to emphasize that these results have come from a patient population with very heavy baseline transfusion burden. And then, the results were similar for both RS-, as well as RS+ patients. These similar results are obtained in our IMerge phase three.

We believe imetelstat will be highly differentiated and very competitive treatment for the lower-risk MDS patient population. Moving on to myelofibrosis. In his earlier remarks, Chip mentioned that in the IMbark phase two trial, the median overall survival was 28 months. These compared very favorably to the median OS of 13 to 16 months in the medical literature.

The median OS also compares favorably to the OS of 12 months, observing real-world data analysis of relapsed/refractory MS patients, who are treated the best available therapy and they were carefully matched with our imetelstat treated patients in IMbark. In addition to the overall survival, patients in IMbark experienced other important clinical benefits, including symptom improvement, screen volume reduction and bone marrow fibrosis improvement. These clinical benefits have been correlated to the improvement in overall survival. Based on these data and after conferring with FDA, we opened IMpactMF in December, which was one quarter earlier than expected.

As mentioned, the IMpactMF is the first and today's only MF phase three trial with overall survival as a primary endpoint, which will be a key differentiating feature compared to other drugs in late-stage development for this population of patients. The same dynamics affecting enrollment in IMerge phase three are also affecting enrollment in IMpactMF. And in addition, we've seen start-up of numerous other clinical trials in MS that will compete with IMpactMF patients. We're using enrollment boosting strategies for IMpactMF, similar to those we have employed in IMerge phase three.

These include expanding the number of countries and sites; engaging more clinical science liaisons; and utilizing a social media campaign. Under current planning assumptions, we expect that IMpactMF reach full enrollment in 2024. And that the internal analysis may also occur in 2024 and the final analysis in 2025. Let me expand a bit on this timeline.

The reason that interim analysis could occur in 2024 because the primary endpoint of the study is overall survival. As a result, the timing of the interim analysis will be based on reaching a certain number of test events. These events will accrue throughout the enrollment period. It is possible that the number of events required to conduct the interim analysis could occur before enrollment is complete.

I'd like to end up my remarks by noting that we're reporting very important data linked to the mechanism of action of imetelstat that maybe responsible for this remarkable disease-modifying activity of the drug we've seen in our phase two trials low-risk MDS and MMF. In low-risk MDS patients, we've observed reductions in key driver mutations at a molecular level and depletion of psychogenetic abnormalities, that indicates imetelstat kills malignant stem and progenitor cells by targeting Telomeres. These molecular data were directly correlated with a clinical benefit of transfusion independence, providing strong evidence of disease-modifying activity of imetelstat. In IMbark, we also saw significant dose-dependent reductions in the mutation burden of key driver mutations for MF, as well as improvement in bone marrow fibrosis.

These data were also correlated with the improved overall survival observed in the IMbark trial, further strengthening the evidence of the disease-modifying activity of imetelstat. We believe that the clinical benefit of durable transfusion independence in low-risk MDS and improvement in overall surviving MF along with a molecular data and their correlations. Highlights and magnitude of imetelstat's unique mechanism of action of Telomeres inhibition and provide strong evidence that imetelstat alters the course of M&A. As a result, we have further confidence that we will have potential success in both IMerge phase three and IMpactMF.

I'd like to now hand the call back to Chip to review the current MDS MMF marketplaces. Chip? Chip, we cannot hear you. There's something with your line?

John Scarlett -- Chairman and Chief Executive Officer

Let's try it, again. Thanks, Aleksandra. Historically, there have been few new treatments for hematologic malignancies, especially myeloid malignancies. However, in 2020, we saw a new approval for luspatercept in low-risk MDS and several new approaches being tested for MF, including many combination therapies.

First, let's discuss last year's approval of luspatercept, trade named REBLOZYL in low-risk MDS. This approval took place in April 2020 based on a phase three trial in non-del(5q) lower-risk MDS patients who are relapsed or refractory to ESAs and naive to HMAs. This trial enrolled only RS+ patients. The launch of REBLOZYL by Celgene and BMS appears to be strong, which validates the high unmet need and the market potential for these RS powers of lower-risk MDS patients.

We expect a highly differentiated profile for imetelstat at launch and the lower-risk MDS market. In the patient population of our IMerge phase two trial that we targeted, as described by Aleksandra, we've seen clinically meaningful transfusion independence across multiple MDS subtypes, including both RS+, as well as RS- patients, low and high transfusion burdened patients in patients with low and high EPO levels. Because of this differentiated and advantageous profile, we continue to expect imetelstat to play a significant role for this lower-risk MDS patient population. For the MS landscape, Jakafi, ruxolitinib, remains the primary frontline treatment.

Although the number of investigational treatments, including combination therapies, has increased over time, these treatments are either another JAK inhibitor or a combination with a JAK inhibitor. They continue to be focused on spleen, symptoms or anemia improvement. These are certainly helpful, but do not address the fundamental problem of continued disease progression in these patients, which results in dismal survival. Eventually, the majority of MF patients are or become nonresponsive to a JAK inhibitor.

As such, there remains a key unmet need of overall survival in JAK inhibitor nonresponsive patients. As the only therapy in development that is not a JAK inhibitor or used in combination with a JAK inhibitor, imetelstat has a clearly differentiated profile, due to its potential to extend the lives of patients who either are or have become nonresponsive to a JAK inhibitor. Next, I'd like to say a few words on our pre-commercial planning and activities. With top line results expected to be available from the end of 2022 to the first half of 2023 and assuming the results of IMerge phase three are supportive, we plan to submit the completed NDA in 2023.

In planning for those events on that timeline, in 2021, we've begun NDA readiness activities for imetelstat and lower-risk MDS. That includes starting long lead time activities to validate drug substance and drug product manufacturing processes that are needed to keep meet standards for regulatory approval and to enable the future commercial production imetelstat.We'll also begin drafting nonclinical content through the application this year. In addition, we'll invest in building the appropriate infrastructure to support a high-growth in commercial stage companies. Other 2021 preliminary commercial activities include preparing the market by increasing awareness of imetelstat's differentiated profile and building our commercial team and internal infrastructure to support commercialization.

However, spending on our commercial launch plan is stage gated to positive top line results in IMerge. In conclusion, before opening the call to questions, I'd like to reiterate our commitment to Geron's vision of being recognized as a leader in the treatment of heme malignancies. In support of that vision, in 2021, our plan is to complete enrollment in the IMerge phase three trial, advanced clinical site initiation and patient enrollment in the impact MS trial, present further data and analyses from the phase two IMerge trial at medical conferences, and begin the NDA and commercial readiness activities I just described. We have a strong team in place that has the expertise to advance imetelstat development and transition to the commercial stage, and having the financial resources to support our plans, we strongly believe our efforts will help establish Geron as a leader in hematologic malignancies, thus creating long-term shareholder value.

And with that, we'd now like to answer your questions. So I'll call -- turn the call back over to the operator.

Questions & Answers:


Operator

[Operator instructions] We'll take our first question from Chad Messer with Needham.

Chad Messer -- Needham & Company -- Analyst

Great thanks. Thanks for the update. Thanks for taking my questions. I just start with a little bit of drill down on COVID impact, everything you said about patients and sites obviously makes a lot of sense what's going on in the world today.

But in your prepared remarks, Chip, you talked a little bit about the primary problem kind of being patients showing up for sites. And then in the press release, there's some additional discussions about site personnel, I guess, site personnel. I was wondering to what extent these two things are playing off relative to each other. I mean to me, and maybe I'm naive, it seems the patient interest in showing up is the most obvious to normalize with COVID and that site things may be more complicated, I could even be wrong about that.

But just wondering if you could give a little bit more insight on the relative impact of those two things, which are both, in my mind, logically impacted by COVID.

John Scarlett -- Chairman and Chief Executive Officer

Yes. That's a really perceptive question. Thanks, Chad. I think I'm going to turn it over to Aleksandra, who's certainly the closest of all the people on the call to the question.

She's in rather constant contact with these sites and our team is, of course. So Aleksandra, maybe you'd like to comment on these two different variables that Chad brought up.

Aleksandra Rizo -- Chief Medical Officer

Sure. Thanks for the question, Chad. I mean you are spot on. The two main issues that we are seeing is really the patient reluctance to participate in clinical trial, which actually may require more frequent visits to the hospital, right, than they would like to during COVID time.

And the second one is really the availability of site personnel, which appear to be busy maintaining trials with, again, multiple procedures during COVID time. So it's really a mixture of these two variables. And it's -- we do expect that as we spoke as the COVID pandemic winds down and with the vaccination, hopefully, patients feel again comfortable to come to clinical -- to come to the clinic and participate in clinical trials. But those are the two key reasons.

Yes.

Chad Messer -- Needham & Company -- Analyst

OK. Yes. No, that makes a lot of sense. And then, this next one, well, I definitely have a comment.

Maybe there's a question in there. So it's really interesting that -- especially when we hear about your ASH data and you talk about justifying OS as the OS benefit that you've seen, and I get it, it's single-arm, so that maybe the justification comes with kind of validating it in that context. But with things like spleen volume and symptom scores, in one way of thinking spleen volume and symptom score should be out there justifying their value in terms of OS, in my mind. So, I guess, that was the comment.

And then the question, and you guys -- you touched on this a little bit. But I mean, talk a little bit more, and I know MF is such a unique disease in terms of the endpoints that are looked at for JAK inhibitors and other standard of care therapies, but why is it that where you have to work so hard here to convince people that OS benefit is important.

John Scarlett -- Chairman and Chief Executive Officer

I'll take the first part, and then I think Aleksandra, again, would like to probably comment on this. I don't think we feel that there's any need to justify the OS benefit. I think it's plain and simple and incredibly obvious. I think we make the point and perhaps our continued commentary on this could be taken the wrong way.

But I think we're trying to make the point that we're the only drug that we're aware of that is actively engaged in the phase three trial that will, in fact, use OS as an outcome. And it takes some courage to do that, right? These are long trials. You have heard the date, they require a fairly large number of patients. And it's breaking out of the mold.

Most people just do a landmark analysis at a certain number of months after being treated with a combination, usually containing a JAK inhibitor and a new drug or simply new JAK inhibitor alone, and you're kind of done. But what you don't see are the real benefits of changing the course of the disease. And Chad, we think that that's the big news, big story and frankly, the big benefit of this drug. I don't think anybody else has any kind of data like we do in that regard.

So that's been our primary focus on why we've tried to talk about OS more than anyone else because we -- and we also have the correlations of the changes in the course of the disease both clinical and more importantly, perhaps, in some ways, molecularly with the actual improvement in OS in our phase two study. So I hope that that puts it in some context. Aleksandra, I don't know if there's anything else to add or Chad, if you would like to jump back in, that's fine.

Chad Messer -- Needham & Company -- Analyst

No. Look, those are really helpful comments in context. Thank you.

John Scarlett -- Chairman and Chief Executive Officer

Sure. Anything else?

Chad Messer -- Needham & Company -- Analyst

That's it for me.

John Scarlett -- Chairman and Chief Executive Officer

Thank you. OK. Go ahead.

Operator

Your next question is from Justin Walsh with B. Riley Securities.

Justin Walsh -- B. Riley Securities -- Analyst

Hi. Thanks for taking my question. Can you provide any color on feedback that you've received from your initial marketing research and outreach efforts? How either our MDS versus MF physicians and patients for new treatment options? And how they reacted to in the imetelstat's profile?

John Scarlett -- Chairman and Chief Executive Officer

Right. Well, I'm going to let Aleksandra talk about the individual physicians that we've spoken to. We've done market research, and we're in the process of planning for additional market researches here that will really drive into those points, Justin. But I think that the benefits of MDS -- in MDS are really quite evident to a lot of physicians, particularly those who take care of more ill patients.

Remember that all of our patients have very high transfusion burdens. And that's an area that can be particularly difficult for these physicians to get traction with. Now they've certainly adopted or they're in the process of adopting luspatercept. And we, again, we call that out, and we think that's good because prior to luspatercept coming on the market, there hasn't been anything new since the HMAs over 10, 12 years ago.

So I think that the rapid uptake has been good, but there's a lot of room left for a drug like an imetelstat that does a bunch of things. One, we treat RS- patients, as well as RS+; two, we can treat patients with very high baseline transfusion burdens and still get excellent outcomes; three, the durability, repeat it, the durability, the durability of imetelstat's activity in these patients is really dramatic and far greater than anything we've seen, at least in print or at meetings from the folks studying luspatercept. So I think that those then factor into the underlying cause of all of this, which is when we see decreases in SF3B1 and decreases inside genetic abnormalities, it's pretty clear that we have disease-modifying activity going on. I won't characterize other products in low-risk MDS, but all of those are really powerful differentiating factors.

And I think that they'll play very, very well. Aleksandra, do you want to comment on the specifics of investigator interaction and KOL interaction because you're very close to a number of resource.

Aleksandra Rizo -- Chief Medical Officer

Sure. Sure. I can talk about that. I mean we obviously are in very close contact with participating PIs, as well as key opinion leaders.

And I can just reiterate. There is really a great enthusiasm for a drug that works across different subtypes of low-risk MDS. That's to start with, right? So for them, there's just the fact that they don't need to subsize whether you RS+ or RS-, makes their clinical and every day work, very easy, right? I mean we were not subtyping for RS positivity prior to REBLOZYL's approval, let's put it that way. So this kind of is one convenience for that, right? And then, I mean, the fact that we have durability of 20 months versus seven months of our already approved drug that is doing very well on the market is really another convenience, if you will, for patients.

You don't have to come back to the clinic for multiple transfusions to which they're used to prior to treatment. And I have to say something and really often discuss this internally. I mean, what really makes investigators excited is the molecular data. It's really -- and this was -- that's maybe even the best reason why the paper ended up in JCO.

So it's really the decrease in not only SF3b1. SF3b1 is just an example that we are using here to illustrate the effect. But it's really multiple mutations that we've seen and also cytogenetic rate decrease in these patients that may believe our KOLs, NPIs that imetelstat is really altering the course of disease in low-risk MDS patients. Same goes, Chip, you answer for MDS.

I don't know, Jason, if you wanted to cover for MS, but it is the same pretty much is really the molecular data. And I mean and Chad also a little bit to go to your question, right, about the OS. I mean data has been evolving and the agencies has been more receptive to different endpoints, right? We started with SVR as Jakafi was on the market for so long. But as new data with new compounds, right, show that we can improve anemia with one drug.

We can improve symptoms, right? New endpoints has been established. And now we come with OS. We had a question, that the crown of the endpoint, I mean, the ultimate endpoint of every clinical trial, right? So when you show such data granted at the moment, it's just from two different doses of imetelstat, enthusiasm is high. I don't think we had leads to justify the OS as an endpoint to any of our investigators nor to regulators so far.

So we remain enthusiastic. It's long, and that's what makes it a challenge. It's a long study, right? It's a different endpoint. But other than that, there's really no other reason to believe that we have any questions about the data.

Justin Walsh -- B. Riley Securities -- Analyst

That's very helpful. Maybe just a quick follow-up to that. So one, could you maybe quickly just remind us of how many of the low-risk MDS patients RS+ positive versus RS-? And do you think that there could be potential for patients to use luspatercept and imetelstat in sequence if they fail therapy with one or the other?

Aleksandra Rizo -- Chief Medical Officer

So typically, the numbers for RS+ patients in the literature range anywhere from 10to 25%, right? It depends which paper you take, right? So let's say most, it's a quarter of the patients are RS+, right? So major -- a lot of the patients are RS-. And again, as we've spoken multiple times, we work across both post subsides. So I think that was one quick question. And can you remind me what was the second part of your question?

Justin Walsh -- B. Riley Securities -- Analyst

Yes. Could -- is there a potential to use luspatercept from subtyping treatment?

Aleksandra Rizo -- Chief Medical Officer

So for RS+ patients, right, potentially, right, but for patients that are heavily transfused, no, I really don't know, right, what would be the clinical preference, I would say.

Justin Walsh -- B. Riley Securities -- Analyst

Thank you very much. That's it for me.

John Scarlett -- Chairman and Chief Executive Officer

OK. Thanks. Thanks, Justin.

Operator

Your next question is from Stephen Willey with Stifel.

Stephen Willey -- Stifel Financial Corp. -- Analyst

Yeah. Good afternoon. So maybe just with respect to the IMpactMF guidance. So I'm just kind of curious as to there's obviously a lot of competitive happenings within the space.

And I'm just kind of curious as to how the guidance if at all contemplates the competitive environment in terms of competition for some of these post-RUX patients? I guess specifically just given the number of trials we're kind of seeing within that setting.

Aleksandra Rizo -- Chief Medical Officer

Yes. That's a great question, Steve. I mean just since we announced the study, there had been three new trials -- phase three trials in MS, right, that had been started. So competition is really high.

For us, at this moment, it's difficult to give a very precise guideline. But as you can imagine, we have conducted a study feasibility. And base -- and that visibility takes into account COVID, as well as competitive trials. So that's how -- based on the current knowledge we have, our current planning assumptions are that we will reach the full enrollment in 2024, which is a different guidance than what we've given so far.

Stephen Willey -- Stifel Financial Corp. -- Analyst

OK. And then, maybe just going back to IMerge for a minute. And Chip, you had made the comment with respect to luspatercept availability potentially impacting patient enrollment into the study. So is there a scenario whereby IMerge maybe ends up representing kind of over enrichment of RS- patients? And do you think that there is any potential labeling or unifications as a result of that? I'm just kind of curious to get your opinion there.

And just whether or not you have kind of real-time insight into the baseline characteristics of patients that are coming into the study if that's something that you're seeing?

John Scarlett -- Chairman and Chief Executive Officer

Again, I think Aleks is in the best position to answer those questions. Go ahead.

Aleksandra Rizo -- Chief Medical Officer

Yes. So I'll start with the last one, Steve. I mean we have no insight into what type of patients are being enrolled in the study because it's a double-blind, placebo-controlled study, right? So it's very difficult to -- not very difficult, it's impossible to comment or to know what patients are enrolled. Now, your first question if luspatercept might or luspatercept approval might have the impact on luspatercept, right, might have impact in a way that we now enroll RS+ patients only -- sorry, RS- patients, the other way because they will be treating.

I don't think so. Remember, luspatercept has just been approved. It will be used on patients, I assume, for the RS+ patients. They would initially be treated with luspatercept and [Inaudible].

So I honestly do not think, right, that we will end up in reaching for one or for another patient population. And therefore, I don't see a problem in the labeling I mean, at the moment.

John Scarlett -- Chairman and Chief Executive Officer

Steve, I think also --

Aleksandra Rizo -- Chief Medical Officer

And Chip, I don't know --

John Scarlett -- Chairman and Chief Executive Officer

Yes. Yes, Steve, I think also we should comment that when we talk to investigators, their views on the -- these are really quite different drugs, right? I mean the effects of imetelstat in high-transfusion burden patients, greater than four units and especially greater than six units is quite dramatically different, at least if you look at sort of the phase two comparisons to phase three comparisons between the two drugs. So I think that there's probably so many different ways to cut this. I agree with Aleksandra.

I think we'll be surprised to see a meaningful enrichment of one RS+ versus RS-. And I think we'll be surprised. But we don't know yet, and we'll see.

Aleksandra Rizo -- Chief Medical Officer

And I would just -- as you were talking Chip, -- sorry, Steve, I just want to answer. I mean we involved about 50% on our trial before luspatercept became available or reimbursed in the European country, where most of our sites are. So I bet, we do have sufficient number in those stations that are RS+ as well RS-.

Stephen Willey -- Stifel Financial Corp. -- Analyst

Very good. That's a fair point. Thanks for taking my question.

John Scarlett -- Chairman and Chief Executive Officer

Sure. Thank you.

Operator

Your next question is from Tom Shrader with BTIG.

Tom Shrader -- BTIG -- Analyst

You kind of just talked about my question, but you see no reason to stratify for RS+ versus RS-. Kind of Chip to your point that these patients either physicians would know are going to get almost nothing out of luspatercept or probably did get almost nothing out of luspatercept. Is that accurate? And you just don't think it confounds your study much?

John Scarlett -- Chairman and Chief Executive Officer

I think the question, if I understand it, Tom, is whether we're stratifying in the analysis for RS+ versus RS-, and stratification, in this case, usually, would mean if you were stratifying in the randomization. We're not stratifying at least in the randomization. Will we look at the effects of the subtypes? Absolutely, of course, we will. So we'll look at it, but we're not preferentially making sure that we take a specific group.

I mean, I need to say this, we don't completely understand why luspatercept has this effect in -- and appears to have this effect, a big enough effect that Acceleron and Celgene decided to really restrict their phase three -- their initial phase three trial MEDALIST study to RS+. But what I can tell you is that when we look at our data, it doesn't really matter whether you're RS+, RS-, you get very similar results. So I think that's the real bottom line for us. And I think that will show equally good results in either group.

Tom Shrader -- BTIG -- Analyst

OK. And then, there's kind of an interesting comment about a reasonable R&D build going forward. Is -- are you still looking -- looking for a way forward in AML? Is that still on the table? Are you looking for a subgroup that makes a lot of sense? Or am I misreading the --

John Scarlett -- Chairman and Chief Executive Officer

Yes. No. I mean let's just say this. I don't know that the R&D build necessarily reflects that.

But what it does reflect is a maturing development organization for a drug that's going to be on the market and however many years. And one that we think has a very unique mechanism of action as well and has properties and capabilities that aren't shared by other products. So we'd be crazy not to try to take advantage of that. And I think that's kind of the real answer.

I don't think we're prepared to talk today about the specifics of what the next indication would be or when it would come or how much it will cost or any of that or how many people will be required to support it. But we certainly have are going through the Asteria line of hematologic malignancies we're certainly interested in putting more in our plates and simply low-risk MDS and MF and relapsed/refractory MF, for that matter. So I think that you can assume that we have a very keen interest in that. But we'll just have to wait a little bit longer for us to really come out and do the -- have the commentary that I think you're looking, Tom.

Tom Shrader -- BTIG -- Analyst

OK. Great. Thank you.

Operator

This concludes our Q&A session. I will now turn the call back over to Dr. Scarlett for closing remarks.

John Scarlett -- Chairman and Chief Executive Officer

Well, thanks a lot. That was a very spirited discussion, which I think we really appreciate and thank everyone who participated. We thank all the people who listened to the call, and we hope you have a good rest of this week and onward. And we will talk to you again truly at the next quarterly earnings call.

Thank you all very much for participating. Bye-bye.

Operator

[Operator signoff]

Duration: 53 minutes

Call participants:

Olivia Bloom -- Chief Financial Officer

John Scarlett -- Chairman and Chief Executive Officer

Aleksandra Rizo -- Chief Medical Officer

Chad Messer -- Needham & Company -- Analyst

Justin Walsh -- B. Riley Securities -- Analyst

Stephen Willey -- Stifel Financial Corp. -- Analyst

Tom Shrader -- BTIG -- Analyst

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